1. Field of the Invention
The invention relates to a nonaqueous secondary battery.
2. Description of Related Art
Japanese Patent Application Publication No. 2006-128091 (JP 2006-128091 A) discloses a nonaqueous secondary battery (specifically, a lithium-ion secondary battery) described below. Specifically, a secondary battery is disclosed, which is provided with an electrode body having a positive electrode, a negative electrode, and a separator, a battery case that houses the electrode body, and a one-way valve provided in a wall part of the battery case. The one-way valve is a valve that communicates with inside of the battery case and allows gas to flow from inside to outside of the battery case. Specifically, the one-way valve is configured as follows. In a case where internal pressure of the battery case is lower than a given value, a communication passage that allows outside and inside of the battery case to communicate with each other is kept closed by a valve body, and, when internal pressure of the battery case reaches the given value, the valve body releases the closed state of the communication passage, thereby discharging gas in the battery case outside through the communication passage. Thereafter, the communication passage is closed again by the valve body.
JP 2006-128091 A describes that the valve body is formed from rubber or resin. In the case where the valve body is formed from rubber or resin, even when the valve body closes the communication passage, moisture outside the battery case (for example, in the atmosphere) could permeate the valve body and enter the battery case. Thus, performance of the nonaqueous secondary battery could be deteriorated.